Autoradiographic model experiments with 67Ga and 99mTc.

In order to evaluate the feasibility to localize correctly 67Ga citrate and 99mTc pertechnetate in tissues, the resolution of these radioactive compounds were measured in a model system using four different autoradiographic techniques, wet as well as dry. Wet autoradiographic techniques gave an almost complete loss of 67Ga. In deparaffinized sections of fixed and paraffin-embedded tissue the remaining 67Ga, which was probably bound to proteins, gave a resolution of 2.6 mu. 99mTc was either completely lost in wet techniques or the procedure could not be performed at all because of the very short half life of 99mTc. The resolution of 67Ga in a dry autoradiographic technique (according to Stumpf) was 6.9 mu and the resolution of 99mTc 22.6 mu. The technique in which frozen sections are thawed on dry film and consequently dryed, gave slightly better resolutions than the dry technique (according to Stumpf) with 67Ga as well as 99mTc. It is concluded that for the histological localization of 67Ga and 99mTc a dry technique is required. However, the use of a wet technique can be considered, provided a loss of the radioisotope is acceptable and the procedure is controlled by a dry technique.